1. Field of the Invention
The present invention relates to ink for ink-jet recording and process for carrying out recording on a recording medium with its droplets, and, particularly, to ink for ink-jet recording and an ink-jet recording process using the same that can perform good printing also on copying paper, report paper, notebooks, letter paper or the like generally used in offices.
2. Related Background Art
Hitherto, ink having quite a variety of composition has been reported in respect of ink for ink-jet printers.
In particular, detailed researches and development have been made from both viewpoints of composition and properties in respect of ink to be used for paper or cloth as the recording medium.
However, the conventional ink for ink-jet printers has had some problems, and it has been a greatest problem that the paper such as notebooks, report paper, copying paper and letter paper generally used in offices can not be used for the printing.
More specifically, if printing is carried out on the variety of the paper mentioned above with use of the conventional ink for ink-jet printers, the ink received for print runs and spreads over the paper along its fiber, so that the shape of dots may become irregular to cause the so-called feathering (or ink spreading). Accordingly, it has often occurred that thin ruled lines, small letters, complicated chinese characters defined as JIS second standard, etc. are unclearly printed and illegible.
Moreover, the above-mentioned paper is applied with a treatment called "sizing" in a paper-making step to suppress the occurrence of feathering when writing is performed with writing utensils with use of usual water-based ink for fountain pens. Accordingly, since in printing with ink-jet printers, the ink can not readily permeate into the paper and the printed part can be dried only, with poor drying performance, there has been the problem that print is rubbed with a cover of the printer and made unclean or hands are stained with ink when the print is touched.
Various improvements have now been attempted for the purpose of preventing the feathering and improving the drying performance of print. For example, Japanese Laid-open Patent Publication No. 57862/1981 discloses a method in which the pH of ink is made strongly alkaline, or the like method; Japanese Laid-open Patent Publication No. 29546/1980, a method in which a large amount of a surface active agent is added into ink; and Japanese Laid-open Patent Publication No. 108271/1983, a method in which an ink being solid at room temperature is heated and turned liquid to carry out recording.
However, the method in which the pH of ink is made strongly alkaline may be dangerous if the ink is touched by hands, and has disadvantages such that both the feathering and drying performance are not in good states with regard to the paper employing a certain kind of sizing agents. In the method in which a large amount of a surface active agent is added, there have been encountered the troubles such that the feathering may occur very frequently depending on the type of paper, the ink moves backward from the face of an orifice depending on the conditions for a print head, causing interruption of ejection of ink, or, on the contrary, the whole face of the orifice is wetted resulting also in no ejection of ink.
In the method in which an ink which is solid at room temperature is heated and turned liquid to carry out recording, though effective to a certain extent in respect of the feathering and drying performance of print, there have also been caused the problems that it requires, in designing a printer, a device for feeding ink while dissolving the ink or a heating unit provided in the printer head, resulting in making the printer large in size, and thus leaving problems in both the cost and ink-handling.
In addition to the above, various improvements have been attempted, but, at present, nothing has been known as to the ink and recording process that can settle all the above-mentioned problems of feathering, drying characteristic of print, large-sized print head, etc.